US2127633A - Smelting of zinciferous materials - Google Patents

Description

Aug. 23, 1938. H, NAJARIAN 2,127,633

SMELTING OF ZI NCIFEROUS MATERIALS Filed May 8, 1955 Patented Aug. 23, 1938 UNITED STATES SMELTING OF ZINCIFEROUS Herand K. Najarian, Beaver, Pa., assignor to St. Joseph Lead Company, New York, N. Y., a corporation of New York Application May 8, 1935, Serial No. 20,507

9 Claims.

ducing agents, together with any desired modi-- fying agents, may be brought into a condition 1 for eflicient smelting and the values contained therein economically separated.

The invention comprises forming zinciferous materials and carbonaceous materials into concretionary aggregates by contacting solid nuclear particles with finely divided zinciferous and carbonaceous materials while subjecting the nuclear particles to continuous rolling and subjecting the concretionary aggregates to a smelting temperature.

A preferred method of making the concretionary aggregates is described in application Serial No. 20,505 filed May 8, 1935, and suitable apparatus 'formaking the concretions is described in application Serial No. 20,506, filed May 8, 1935.

The invention will be described for the purpose of illustration with reference to the accompanying drawing showing a flow sheet of one embodiment of the method of the invention.

In the drawing, l is a ball mill wherein zinciferous materials, such as calcined zincsulphide ore, are ground together with a reducing fuel, such as coke, and fluxes or other desired modifying agents, preferably, to a fineness of about- 200 mesh U. S. standard screen. The ground materials are conveyed by belt conveyor 2 to screw conveyor 3 which carries the materials into rtary drum 4. Nucleus material, for example,

lumps of coke about to inch in size, is fed through nozzles 8.

By the action of the alternate spraying with binder liquid and coating with the finely divided ore and coke, and the continuous rolling in drum 4, the ore and coke are built up into a shell around the nuclei, as described more fully in the applications above referred to, forming concretions of, for example, 1 to 1% inches in diameter.

A typical concretion is shown in Fig. 2, where- ,in I represents the nucleus, for example, of coke,

and 2 represents the shell of zinciferous and carboniferous material.

The formed concretions are then passed 5 through drying chamber ill by means of conveyor 9 and thence preferably into preheater I I wherein the concretions may advantageously be heated to nearly the reduction point, for example, 600 to 700 C., by any suitable heating means. By 10 this operation the volatile content of the binder used, or of the carbonaceous material, is driven off.

The preheated concretions are then fed into a furnace l2 which may be ail-externally heated retort, a blast furnace, an electric arc furnace, or an electric resistance furnace. The furnace shown inthe drawing by way of example is an electric resistance furnace of the type described in U. S. Patent 1,7 75,591 to Gaskill.

When the concretions have reached smelting temperature in the furnace, zinc vapor is freely and evenly evolved and may be condensed to metallic zinc in condenser l3, or oxidized to zinc oxide at M.

The residues may be discharged from the retort or furnace by any convenient means, as, for example, rotating table IS. The residues may then be separated and any substantial values therein returned to the process.

The following are several examples of formulas for zinciferous concretions, which are illustrative of the wide variety of zinciferous materials which may be utilized in the invention:

Example No. 1

Compo- I Material smon Weight Perce'n Pounds 99% l00M. Zn 69. 900

see

Zn Fe Coke, ground with ore (reclaim) 91% 200 M. l00

Cokenuclel +a s" -5/s" Example No. 2

Material Composition Weight 7 Percent Pounds Droes Zn 65.00 120 Other metals 27. 00

Drop ZnO Zn 72.00 317 Other metals 21.00

Magnetic zinc residue Zn 27. 20 413 Bio; 25. 40 Fe 18. 70 O 7. 20

Coke ground with ore 150 Binter nuclei Zn 59. 210

Suiphite liquor, 10 RmmA 185 Example N0. 3

Material Composition Weight Percent Pounds Drop zinc oxide Zn 72.00 260 .Other metals 21.00 C 2. 00

Magnetic zinc residue Zn 27. 20 615 Other metals 4. 00 S10: 23. 40 Fe 18. 70 C 7. 20

Reclaim coke ground with ore Zn 7. 00

Lime rock ground with ore .4 30

Coke nuclei; Fe 3. 00 70 Sulphite liquor, 10 Baum The above Exampes 1-3 are useful in the manufacture of lead-free zinc oxides, zinc metals, and other zinc products.

Examples 4, 5 and 6 are used in the manufacture of leaded zinc oxide and relatively high lead zinc metal.

Example No. 4

Composi- Material on Weight Percent Pounds Flue dust Zn 54. 00 890 Pb 15. 10 Fe 7. 00 S 1. 10

Reclaimed coke Zn 1. 00 110 Coke nuclei 70 Sulphite liquor, 10 Baum 185 Example N0. 5

Material Composition Weight Percent Pou'mix Flue dust Zn 54. 390

Pb 15. 10 Fe 7.00 s 1.10

Reclaimed coke Zn 7. on

Sinter nuclei Zn 59. 80 210 Metallica 9. 40 Si0 8.80 Fe 7.90 S 10 Sulphlte liquor, 10 Baume 185 Example No. 6

Material Composition Weight Percent Pounds Flue dust Zn 54. 00 1000 Pb 15. 10 Fe 7. 00 B l. 10

Sinter nuclei Z11 59.80 210 Metallics 9. 40 SiO; 8.80 Fe 7.90 10 Bulphite liquor, 10 Baum 165 and temperature necessary to complete reduction are materially reduced. For example, in the or- Y dinary Belgian type zinc retort, reduction of the zinc-bearing concretion will be complete in from 6 to 8 hours at a temperature of 1200 0., contrasted with a time of from 16 to 18 hours when smelting the ordinary loose charge which is commonly used.

Furthermore, due to the intimate mixture of the carbonaceous and zincifero'us materials, the temperature at which reduction reactions have comparable efliciencies would be 975 C. for the 'concretions and 1225 C. for the loose charges of ordinary practice. This is due to the fact that in the reduction of an aggregate, such as 'a lump of ore, sinter, or an agglomerate of ore alone, the reduction progresses from the outside surface inwardly, the difliculties of bringing about contact with the carbonaceous material, or of effecting carbonaceous gas penetration being greatly increased. as the size of the particle increases, inasmuch as the inert materials carried by the ore when it is in the form of lumps or agglomerates having appreciable size, serve to segregate as reduction proceeds on the surface of the particles, preventing free carbon contact and making the penetration of the carbonaceous gases diflicult. Therefore, the time and temperature required for the final efflcient reduction of such ores is greatly increased over that required by the finely ground .metalliierous materials intimately mixed with finely ground carbonaceous materials in the concretions of this invention.

With a carbonaceous nucleus, considerable vapor pressure at the temperature of I reduction must be exerted from that direction and reduction proceeds rapidly, inasmuch as the novel conditions of structure of the concretion promote th realization of nearly ideal reduction.

The concretions being spherical, or nearly so, in form, the space between the bodies for the circulation of the gases and vapors is at a maximum, thus resulting in a very rapid heat transfer from one part of the retort to the other and the assurance, due to the open charge, that local pressures will not be built up, which seriously impair smeltlug emciency. Inasmuch as, referring particularly to zinciferous ores, the preferable carbonaceous content. is metallurgical coke containing relatively low sulphur and very low residual volatile content, the concretions of the invention may be used in the direct production of the metallic oxides from the volatile metals, and a high grade product obtained, which cannotbe realized, particularly in the manufacture of zinc oxides or the basic lead sulphates by the fuming process, when the raw zinciferous or plumbiferous materials are briquetted with the coking bituminous coals. Inasmuch as the limitations placed upon the coking process by the reduction temperature of these metalliferous materials are such that the volatile content of the briquette or agglomerate cannot be reduced below about 2%, the result is that as this material is subsequently reduced in the smelting furnace, the remaining volatile hydrocarbon of the briquette or agglomerate is distilled off in the reduction process and carried out with the gases and vapors, excessively discoloring the oxides produced by these processes and making them unfit for commercial use in many of the arts. Furthermore, a briquette made without the aid of the flowing or coking coals, or an excessive amount of tar or pitch, has not proved satisfactory in shaft furnaces, due largely to the fact that, although great pressures are used by the numerous briquette pressing devices, the moisture content at the time of pressing must be kept relatively low, with the result that the particles are not thoroughly wetted, that the binder and the matrix formed by the subsequent reaction due to heat or chemical reaction are poorly distributed, and that when the briquette is highly heated it sands rapidly, causing a loss of furnace porosity and a consequent loss of smelting efficiency due to the difliculties of obtaining uniform heat penetration to all parts of the charge.-

In blast furnace smelting, if the charge consists or concretionary agglomerates, made by using the fuel portion of the charge in the form of lumps of coke, coal, or charcoal as nuclei, and coating them with the finely ground mixture of ores, fluxes, flue dust and the like, improved operation and reduction in fuel consumption are obtained due to the fact that the concretions permit free and more uniform circulation of reducing gases in the furnace while the coating on the fuel inhibits the dissolution of the carbon in the fuel at the upper zones of the blast furnace by ascending carbonic acid gas.

The solid nucleus of the concretion of this invention-whatever it may be composed ofgreatly reinforces the structure and prevents breakage and crumbling.

I claim:

1. A method of smelting zinciferous materials which comprises forming concretions of finely divided zinciferous material and carboniferous material about solid nuclei of a material entering into the smelting reaction and subjecting the concretions to smelting temperature. I

2. A method of smelting zinciferous materials which comprises forming concretionsof finely divided zinciferous material and carboniferous material about solid nuclei of reducing fuel and subjecting the concretions to smelting temperature.

3. A method of smelting zinciferous materials which comprises forming concretions of finely divided zinciferous material and carboniferous ma terial about solid nuclei of coke and subjecting the concretions to smelting temperature.

4. A method of smelting zinciferous materials which comprises forming concretions of finely divided zinciferous material and carboniferous material about solid nuclei of sintered zinciferous material and subjecting the concretions to smelting temperature.

5. A method of smelting zinciferous materials which comprises forming concretions of finely divided zinciferous material and carboniferous material about solid nuclei of a material entering into the smelting reaction, preheating the concretions to below smelting temperature, and subjecting the preheated concretions to smelting temperature.

6. A method of smelting zinciferous materials which comprises forming concretions of finely divided zinciferous material and carboniferous material about solid nuclei of a material entering into the smelting reaction and subjecting the concretions to smelting temperature by passing an electric current through a column of the concretions.

7. A method of smelting zinciferous materials which comprises forming concretions of finely divided zinciferous material and carboniferous material about solid nuclei of a material entering into the smelting reaction, preheating the concretions to below smelting temperature, and subjecting the preheated concretions to smelting temperature by passing an electric current through a column of the concretions.

8. A method of smelting zinciferous materials which comprises contacting solid particles of a material entering into the smelting reaction with finely divided zinciferous material and carboniferous material and with a binder material while subjecting the particles to continuous rolling until a shell of desired size has "uilt up about the solid particles, thereafter continuing the rollinging until a shell of desired size has built up about the solid particles, thereafter continuing the rolling operation until the substance of said shell is well plasticized, indurating the concretions thus formed by heating and subjecting the induratedconcretions to smelting temperature.

K. NAJARIAN.

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